The invention relates to a device for wetting a blood serum bearing film in electrophoretic apparatus, and more particularly, to such device which is adapted to be used in a blood serum analyzer of electrophoresis type.
As is well known, an electrophoretic apparatus achieves a fractionation of serum components applied to a bearing film by the process of electrophoresis. The fractionated components are determined with a densitometer or a photoelectric colorimeter of filter type for the purpose of quantitative analysis thereof. In such apparatus, the film is previously wetted with a buffer solution before a blood serum is applied thereto in order to facilitate the electrophoretic process to occur. Wetting device used at this end is already known. The film usually comprises a film of cellulose acetate while a buffer solution comprises Veronal-Veronal soda solution.
A conventional wetting device is shown in FIGS. 1 and 2, to which reference is made. The device includes a pair of upper and lower conveyor rollers 1, 2 having its surface layer 1b, 2b formed of a sponge material. A vessel 3 contains a quantity of buffer solution 4 such as Veronal-Veronal soda solution, and the pair of rollers are disposed therein so that the surface layer 1b of the lower roller 1 is maintained in immersion in the solution 4. The lower roller 1 has its drive shaft 1a rotatably mounted in the opposite sidewalls 3b of the vessel 3 at a level such that the surface layer 1b is partly immersed in the solution 4. The end of the drive shaft 1a, which is not visible in FIG. 1, extends out of the vessel to be connected with a suitable drive source to be driven for rotation in a direction indicated by an arrow a. The shaft 2a of the upper roller 2 has its opposite ends received in a pair of notches 3a formed in the top end of the both sidewalls 3b of the vessel 3 so as to be rotatable and also movable in the vertical direction. The arrangement is such that the upper roller is maintained in abutment against the lower roller by gravity.
In operation, when a blood serum bearing film 5 such as that formed by cellulose acetate is fed in a direction indicated by an arrow b (see FIG. 2) to be passed between the rollers 1, 2 by rotating the latter in the direction of the arrow a, the buffer solution 4 contained in the surface layer 1b of the lower roller wets the film, thus automatically achieving a wetting of the film.
However, such conventional arrangement suffers from the disadvantage that creases or crimples are formed in the film surface along the feed direction thereof while it passes between the rollers to be wetted with the buffer solution 4. Specifically, when wetted with the buffer solution, the film 5 immediately tends to expand in both feed and width directions. However, because the film 5 is held between the both rollers 1, 2, it cannot expand in the width direction. As a consequence, the width l' of the film 5 after the wetting process (see FIG. 3B) remains substantially equal to the width l before the wetting process shown in FIG. 3A, but creases are formed in the feed direction in order to accommodate for the elongation in the width direction.
The rate of expansion of the cellulose acetate film varies with the film composition, lot and manufacturers, but ranges from zero to several percent, resulting in a relatively large variation from film to film. It is known that the formation of creases will be greater with a film having a greater rate of expansion. The blood serum cannot be uniformly applied to a film having such creases formed therein. In addition, the presence of creases interferes with the electrophoretic process of the serum components, preventing a smooth formation of a fractionated pattern from being formed.